Firstly, there are several threads on this already - keep in mind that this forum has a good search feature.
Secondly, how you kill him depends on your classes and levels. Two good melee warriors can do maybe 300 points of damage a round (more with criticals) and kill the shaman rather fast if they have decent weapons and have put most of their skill points into training for the weapons they are using. A warrior and a mage can kill him almost as easily - the mage hammer spell paralyzes him and the warrior can whack away at him. Two mages have more issues but can suck down mana potions as needed and cast damage spells continuously, keeping the shaman too paralyzed to heal himself with that hammer spell.
I've never done much with rogues.
